Engineering anodes for rechargeable aqueous aluminum-ion batteries

• Main Author: Jia, Beier
• Other Authors: Alex Yan Qingyu
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Chemistry; Engineering; Aqueous aluminum batteries; Anode engineering
• Online Access: https://hdl.handle.net/10356/182222
• Institution: Nanyang Technological University

The increasing utilization of renewable energy sources, including wind and solar power, has created new demands for safe, low-cost, and reliable electrochemical energy storage (EES). Existing EES systems, primarily based on lithium (Li)-ion batteries, face challenges, including the scarcity of Li reserves and safety concerns. Consequently, the development of "beyond Li" batteries has become a research hotspot. Among these, rechargeable aqueous aluminum-ion batteries (AAIBs) have garnered significant attention because of their notable advantages. These include the intrinsic safety provided by aqueous electrolytes, the abundance of aluminum (Al) resources (constituting 8.23 wt% of the Earth's crust), the low cost of Al metal, and its well-established industry. Specifically, employing Al metal as the battery anode theoretically offers a substantial gravimetric capacity of 2980 mAh g−1 and a volumetric capacity of 8046 mAh cm−3. However, the development of Al metal anodes in aqueous electrolytes is hindered by several issues, including surface passivating films that obstruct charge/ion transport, the highly negative deposition potential of Al ions, which induces hydrogen evolution reaction (HER), poor reversibility of Al stripping/plating (ASP), low battery voltage plateaus, and poor cycle stability, all of which diminish the attractiveness of aqueous aluminum metal batteries (AAMBs). This thesis aims to alleviate these key challenges of Al anodes through anode engineering strategies, such as amorphization, composite heterometallic structures, and coating with transition metal disulfides (TMDs). These approaches aim to alleviate passivation, enhance the ASP reversibility, and suppress side reactions like HER and corrosion, thereby improving the voltage plateau, specific capacity, and cycle stability of AAMBs. The first project employs an amorphization approach to alter the potential of Al plating. An amorphous Al (aAl) interface is generated on Al substrates via Li-ion alloying/dealloying. Experimental and theoretical studies reveal that the amorphous structure significantly reduces the nucleation barrier for Al, promoting Al plating in competition with HER. Additionally, it mitigates passivation and enhances interfacial ion transport kinetics. This electrode achieves stable ASP for 800 hours in symmetric cells. Compared to bare Al-based cells, full cells using an aAl anode exhibit a voltage plateau increase of 0.6 V. The second project involves the introduction of secondary metals to composite with Al. Tin (Sn) is chosen as the secondary metal because of its suitable standard electrode potential, work function, and Al compatibility, which aids in Al plating and improves the reversibility of the anode. The Sn–Al laminate (Sn@Al), prepared via iterative folding/rolling procedures, efficiently enhances ASP and minimizes resistance. The Sn@Al electrode exhibits long-lasting cycling for more than 900 hours in symmetric cells and shows outstanding performance when paired with AlxMnO2 or Prussian blue analog cathodes. To improve the performance of the Sn@Al, a polymer layer is utilized to effectively inhibit corrosion. The third project investigates Al anodes coated with four types of TMDs. The results indicate that TiS2 and NbS2 exhibit electrochemical activity in aqueous aluminum sulfate electrolyte, while MoS2 and ReS2 show negligible activity. AAIBs with Al anodes coated with all four TMDs demonstrate higher capacities compared to uncoated Al anodes. This enhancement may arise from two distinct mechanisms. TiS2 and NbS2 could potentially intercalate and de-intercalate Al ions and/or protons, while MoS2 and ReS2 mainly function as protective coatings. These findings reveal the feasibility of using TMD-coated Al as anodes for AAIBs. These findings provide valuable insights into the rational design of Al anodes, advancing the development of high-performance AAIBs for sustainable energy storage applications.